Shiplift
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A shiplift is a modern alternative for a slipway, a floating dry dock or a graving dry dock. A shiplift is used to dry dock and launch ships. It consists out of a steel structural platform that is lowered synchronously by a number of hoists. First, the platform is lowered underwater, then the ship is floated above the platform, and finally the platform is lifted and brings the ship to the level of the quay.
It is important to synchronise the winches. Modern systems use electrical control and drive systems for the winches. Old fashioned electrically driven shiplift systems needed so much starting current that they often could only be used in the weekend when all other electrically equipment was not in use. The modern shiplifts however do not have this disadvantage; they can start the movement in any desired curve.
In general a shiplift is making use of a transfersystem for ships, so that the ships can be transported from the shipliftplatform to a parking place on the shipyard, where the ship can be painted or repaired. In such a way one shiplift can serve in fact dozens of parking places, whereas in general a dry docking installation can only dock one ship.
The transfersystem in general consists out of a number of trolleys or cradles, supported by high capacity steel wheels. The wheels drive on heavy duty rails. The transport can be one directional, but in order to serve more parking places, two directional systems are used. These twodirectional systems make use of a so called traverser carriage or sometimes the wheels of the trolleys can be turned over 90 degrees. Above the wheels often hydraulic cylinders are located so that the ship can be transported upon a so called "fluid bed". The cylinders are also used to lower the ships on a static support, so that the transfer system with the activ elements can be recovered.
